Pre-tensioned Bearing Thrust Washer Friction Coating
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Solution Overview
Problem
Existing bearing arrangements in small electric motors experience relative movement between the shaft and inner ring or outer ring and housing, leading to high-frequency noises and fretting corrosion, which compromises precision and service life.
Innovation Solution
A thrust washer coated on both sides with a layer increasing static friction is used between the spring and the preloaded bearing ring, preventing relative movement and enhancing static friction, thereby avoiding fretting corrosion and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a metal thrust washer is used between the spring and the preloaded bearing ring, then the bearing can be axially preloaded, but relative movement occurs between the shaft and inner ring or outer ring and housing due to insufficient circumferential friction forces
Solution Approach 1:
The patent changes the surface friction parameter of the thrust washer by coating it with a high-friction material. This increases the static friction coefficient between the thrust washer and the bearing ring, preventing circumferential relative movement while maintaining the axial preload function. The coating transforms the low-friction metal surface into a high-friction surface that can transmit both axial and circumferential forces.
Solution Approach 2:
The thrust washer is constructed as a composite component with a metal substrate and a coating layer of high-friction material. This composite structure combines the mechanical strength and dimensional stability of metal with the high static friction properties of the coating material, achieving both axial preload capability and circumferential movement prevention.
2Strength
If the thrust washer is made of metal, then it provides structural strength, but relative movement causes fretting corrosion and high-frequency noises
Solution Approach 1:
The thrust washer combines a metal substrate providing structural strength with a high-friction coating layer that prevents relative movement. This composite structure eliminates fretting corrosion by preventing the micro-movements that cause it, while the metal substrate maintains the necessary mechanical strength to support the axial preload.
Solution Approach 2:
The patent converts the potentially harmful relative movement that causes fretting corrosion into a beneficial stationary connection through the high-friction coating. The coating creates sufficient static friction to prevent movement, transforming what would be a harmful sliding condition into a beneficial fixed connection that eliminates noise and corrosion.
3Force
If axial circlips are used to support the spring, then the bearing can be preloaded, but the circlips rotate on the shaft causing insufficient circumferential forces to overcome bearing losses
Solution Approach 1:
The high-friction coating on the thrust washer acts as an intermediary that enhances the force transmission from the spring through the thrust washer to the bearing ring. The increased static friction coefficient allows the thrust washer to effectively transmit both axial preload forces and circumferential forces, preventing energy loss due to relative movement.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution significantly increases the service life of the bearing by preventing relative movement and reducing noise, while maintaining the motor's dimensions and simplicity of design.
Implementation Method 1
a spring element arranged between the axial stop and the inner or outer ring for generating the axial preload
Implementation Method 2
the thrust washer is coated on both sides with a layer that increases static friction
Data Source
Figure 1~2
AI summary
The present invention relates to a bearing arrangement (1) for an electric motor (2), in particular for a small electric motor. It comprises an axially preloaded ball bearing with an inner ring (3) and an outer ring (4). The bearing arrangement further comprises an axial stop (5), a spring element (6) arranged between the axial stop and the inner or outer ring for generating the axial preload, and a metal thrust washer (7) arranged between the spring element and the inner or outer ring. According to the invention, the thrust washer is coated on both sides with a friction-enhancing layer (8).